JP3623681B2

JP3623681B2 - Method for producing 25-250 micron biaxially oriented polypropylene (BOPP) pearl gloss synthetic paper obtained by three-layer coextrusion method

Info

Publication number: JP3623681B2
Application number: JP01536599A
Authority: JP
Inventors: 林豊欽
Original assignee: 南亜塑膠工業股▲ふん▼有限公司
Priority date: 1999-01-25
Filing date: 1999-01-25
Publication date: 2005-02-23
Anticipated expiration: 2019-01-25
Also published as: JP2000211008A

Description

【０００１】
【発明の属する技術分野】
本発明は三層共押出方式で得られる厚み２５〜２５０ミクロン二軸延伸ポリプロピレンパール光沢合成紙の製造方法に関するもので、とくに三層共押出方法により、それぞれフィーダーを持つトゥイン・スクリュー主押出機１台とフィーダーを持つトゥイン・スクリュー副押出機２台から押出されたポリプロピレン樹脂と無機物の混合押出物を合流させ、１つのＴダイヘッドを経て紙状層または樹脂層／発泡中間層／紙状層または樹脂層の三層シートとし、さらに冷却成形、二軸延伸、コロナ処理、巻取りなどのステップを経て、２５〜２５０ミクロンの厚みを持つ紙状層／発泡中間層／紙状層の三層共押出両面紙状面パール光沢合成紙、紙状層／発泡中間層／樹脂層の三層共押出単面紙状面パール光沢合成紙、樹脂層／発泡中間層／樹脂層の三層共押出両面光沢面パール光沢合成紙を製造し、塗布用合成紙の塗布紙とするものを指す。
【０００２】
【従来の技術】
現在ポリオレフィン合成紙は天然パルプ抄造紙に取って代わろうとしている。ポリプロピレンの二軸延伸フィルムを基材層（中間層）とし、裏表に８〜６５重量％の無機微細粉末を含むポリプロピレン１軸延伸フィルムを紙状層とする合成紙が出願され、実用化されている。王子油化合成紙株式会社は特公昭４６−４０７９４号、特開昭５６−１４１３３９号、特開昭５６−１１８４３７号、特開平３−８７２５５号などの特許出願を提出している。
【０００４】
【発明が解決しようとする課題】
これらの製造方法では、基材層を縦方向延伸装置と横方向延伸装置の間に置き、２台の押出機を利用し、上下フィルムを作り紙状層を完成している。紙状層は横方向にだけ延伸でき、紙状層の強度は低い。紙状層の印刷性を高めるため添加されている無機微細粉末は印刷加工工程において脱落するため、印刷機器を清掃する必要がある。また、一軸延伸で得られた紙状層と二軸延伸で得られた基材層とは総延伸率が異なり、このため加熱時に、紙状層と基材層の収縮率も異なり、紙がウェーブ状に変形してしまう。さらに製造工程と製品品質の安定性を高めるため、２台の押出機で上下フィルムを完成する紙状層の製造工程では生産速度が制限され、延伸後の完成品の幅が最大６メートルにすぎない。単一の紙状層の厚みが少なくとも１０ミクロン（通常は３０ミクロン）必要なため、製品の厚みはつねに６０ミクロン以上となる。さもなくば、製品の厚みが不均一となり、印刷加工に影響が出てしまう。総体的に製造工程の難度が高く、生産コストも高いため、製品が普及しにくく、応用がむずかしい。
【０００５】
【課題を解決するための手段】
上記問題を解決するため、本発明出願人は新しい三層構造合成紙の製造方法を提出する。当該合成紙は紙状層または樹脂層／発泡中間層／紙状層または樹脂層から構成され、発泡中間層のポリプロピレン樹脂混合物を１台のフィーダーを持つトゥイン・スクリュー主押出機から、紙状層または樹脂層の樹脂混合物を２台のフィーダーを持つトゥイン・スクリュー副押出機からそれぞれ押出し、これらの押出物を合流させ、１つのＴダイヘッドを経て三層シートとし、さらに冷却成形、二軸延伸、コロナ処理、巻取りなどのステップを経て、２５〜２５０ミクロンの厚みを持つ三層共押出単／両面紙状面および両面光沢面のパール光沢合成紙を得る。本発明の製造方法は三層共押出方式を採用する。各層の押出物を合流させた後に共押出し、さらに二軸圧延して得られた合成紙は、従来の方法により二軸延伸した中間層に一軸延伸した紙状面を貼付して得られた合成紙とは構造、製造方法とも異なる。同時に副押出機から押出す原料を、無機充填剤を使用した紙状層と無機充填剤を添加していない樹脂層から選ぶことで、紙状層／発泡中間層／紙状層の三層共押出両面紙状面パール光沢合成紙、紙状層／発泡中間層／樹脂層の三層共押出単面紙状面パール光沢合成紙、樹脂層／発泡中間層／樹脂層の三層共押出両面光沢面パール光沢合成紙を製造し、塗布用合成紙の塗布紙とすることができる。
【０００６】
【発明の実施の形態】
本発明の技術内容を明確に示すため、ポリプロピレン樹脂混合物と製造工程（押出し、三層共押出、冷却、二軸延伸、コロナ処理、巻取り）について以下に説明する。本発明の二軸延伸ポリプロピレンパール光沢合成紙は三層構造を有する。その発泡中間層は１台のサイドフィーダーを持つトゥイン・スクリュー主押出機で押出す。アイソタクチック度９７％以上の高結晶性ポリプロピレン３９〜９５重量％、静電気防止剤１〜５重量％を主押出機の前方にあるホッパーで均一に攪拌し、主押出機に入れる。さらに炭酸カルシウム粉末０〜４０重量％と二酸化チタン粉末０〜２０重量％を計量後、１台または２台のサイドフィーダーで主押出機に入れる。主押出機のトゥイン・スクリューで均一に混練した後、樹脂と無機粉末の混合物をＴダイヘッドの中間ラナー（runner）に押し入れる。また、紙状層はサイドフィーダーを持つトゥイン・スクリュー副押出機２台で押出す。ポリプロピレン２０〜９９．５重量％、ポリエチレン０〜１２重量％、静電気防止剤０〜３重量％、粘着防止剤０．５〜３重量％、紫外線吸収剤０〜２重量％を副押出機前方にあるホッパーで均一に攪拌した後、副押出機に入れる。さらに炭酸カルシウム粉末０〜４０重量％と二酸化チタン粉末０〜２０重量％を計量後、１台または２台のサイドフィーダーで副押出機に入れる。副押出機のトゥイン・スクリューで均一に混練した後、樹脂と無機粉末の混合物をＴダイヘッドの両側道に押し入れる。上述の押出機３台からの押出物を合流させ、Ｔダイヘッドで共押出し、樹脂層または紙状層／発泡中間層／樹脂層または紙状層のシートを形成する。二軸延伸、コロナ処理、巻取のステップを経て、厚み２０〜２５０ミクロンの両／単面紙状面のパール光沢合成紙を製造する。本発明の製造方法で製造された合成紙は文化紙に適しており、高結晶性ポリプロピレンを主要原料としている。本発明で使用されるポリプロピレン樹脂は溶融指数（ＭＦＩ）が０．５〜８（２３０℃／２．１６ｋｇＡＳＴＭＤ１２３８）で、大部分がアイソタクチックな均一重合物とする。この種の高分子構造は分子同士が配列正しく結合している。原料の分子量とその分布状況により、パール光沢合成紙の機械強度と品質の均一性を制御することができる。本発明の製造方法で得られたパール光沢合成紙は三層構造を呈している。図１に示す通り、紙状層の紙模倣効果を高めるため、ポリエチレン、無機粉末を配合し、その用量で光沢度、筆記性、印刷性を調整することができる。ポリエチレンのＭＦＩは０．１〜７のものを採用する。ポリエチレンのＭＦＩで紙状面の強度を調整できる。本発明で使用される無機粉末は、発泡中間層の密度を下げる（延伸工程における微細孔発生を利用）ほか、紙状層にプラスチック紙とは異なる優れた筆記性と印刷性をもたらすことができる。無機粉末は炭酸カルシウム、けい藻土、クレー、酸化カルシウム、硫酸バリウム、二酸化チタンなどのグループから１種類または多種類を選んで使用する。その粒径は０．１〜１０ミクロンとし、用量は製品の需要によって決定する。本発明は側方から配合料を給送するトゥイン・スクリュー押出機で製造する。その無機粉末はサイドフィーダーから押出機に入れる。トゥイン・スクリューを利用した押出機で均一に混練することができる。このほか、無機粉末と樹脂を先に混練した複合粒を最前方のホッパーに入れ、各種樹脂と混合した後さらに押出機に入れることもできる。本発明では製品の不透明度、白色度、抗紫外線性を調整するため、二酸化チタン粉末を使用している。本発明の静電気防止剤は、通常の二軸延伸ポリプロピレン（ＢＯＰＰ）で使用されている静電気防止剤をすべて使用することができる。三級アミン類が主に使用されている。三級アミンは電荷移行性を有するため、加工摩擦で発生した静電気を除去することができる。本発明において、合成紙を巻き取る時互いに粘着するため、粘着防止剤を添加する必要がある。通常の二軸延伸ポリプロピレンで使用されているシリカ、クレー、ポリメチルアクリル酸メチルエステル（ＰＭＭＡ）、ガラスビーズなどから１種類を選ぶことができる。本発明で得られるポリプロピレンパール光沢合成紙の比重は０．７５以下であり、混合物の組成比で調整することができる。これは特開平３―８７２５５号の合成紙の０．７９に比べて低く、同じ重さでより広い面積の合成紙を製造することができるため、経済性が高い。本発明で得られる二軸延伸ポリプロピレンパール光沢合成紙は、紙状層／発泡中間層／紙状層または樹脂層の三層構造を有し、物性、生産能力は材料の配合、設備、操作と深い関係がある。通常のポリプロピレン膜の二軸延伸製品は、ほとんどが充填剤を添加していない、透明な製品である。本発明では紙を模倣するため、製造工程において大量の無機充填剤を添加する必要があり、二軸延伸製造工程の生産性、生産能力、品質安定に関して問題を克服しなければならない。本発明のポリプロピレンパール光沢合成紙（厚み２５〜２５０ミクロン）で使用する製造工程の装置とステップを図４に示す。
押出機装置（図４の(1)）：サイドフィーダーを持つトゥイン・スクリュー主押出機１台とサイドフィーダーを持つトゥイン・スクリュー副押出機２台から成る。その温度設定条件は樹脂混合物の組成、ＭＦＩ、結晶度、粘度、生産ラインの速度、製品の厚みによって異なるが、通常は１８０〜２８０℃とする。１８０℃以下では樹脂の可塑化が進まず、Ｔダイヘッドで押出すことができない。２８０℃以上では樹脂が過度に可塑化し、亀裂が入ってしまう。本発明では三層共押出方式で三層合成紙（紙状層または樹脂層／発泡中間層／紙状層または樹脂層）を製造する。Ｔダイヘッドの流道設計により三層の押出物を合流させ、Ｔダイヘッドで三層を共押出する。
冷却成形ロール装置（図４の(2)）：水冷式またはガス冷却式の冷却装置とする。１８０〜２８０℃で三層共押出された溶融共押出物を冷却し、成形する。冷却温度の制御は、その後のステップが順調にいくかどうかを大きく左右する。冷却温度は通常１５〜６０℃に設定し、合成紙板の厚みと生産ラインの速度によりこの範囲で調整できる。
縦方向延伸装置（図４の(3)）：冷却成形を経た紙板を縦方向延伸装置に入れる。先ず１１５〜１５０℃（紙板の厚みと生産ラインの速度で選択する）に加熱し、紙板を軟化させ、さらに低速および高速の２段階で延伸し、合成紙に縦方向強度を与える。また、アニーリングで成形する。縦方向の延伸率は通常３〜６倍に設定する。
横方向延伸装置（図４の(4)）：縦方向延伸処理で薄くなった紙板を１４０〜１９５℃（紙板の厚みと生産ラインの速度で選択する）に加熱して軟化させ、横方向に延伸し、さらにアニーリングで成形し、パール合成紙の部分収縮によりサイズの安定性を高める。通常、横方向延伸倍率は５〜１２倍に設定する。製品の特性により選ぶことができる。
コロナ処理装置（図４の(5)）：コロナ処理はポリプロピレンパール光沢合成紙の物性を改善するために行われ、印刷、塗布、コーティングなどの加工が容易になる。処理効率を２０〜１２０ＫＷとする高周波放電装置（生産ラインの速度により調整）でコロナ処理を行う。これにより表面の湿潤張力は３６〜４８ダイン／ｃｍに達する。
巻取装置（図４の(6)）：鉄パイプを利用し、完成したパール光沢合成紙を巻き取り、幅８メートルの完成品とする。必要により縦または横にカットし、包装して、厚み２５〜２５０ミクロンのロール状またはシート状製品とする。本発明の製造方法で得られた厚み２５〜２５０ミクロン二軸延伸ポリプロピレンパール光沢合成紙における三層の厚みを表１に示す。紙状層と樹脂層の厚みは１〜３０ミクロンの範囲で調整できる。
【０００７】
本発明の技術内容を明確に説明するため、以下に筆記用、印刷用、包装用及び各種用途の合成紙を製造した本発明の実施例を示す。ただし、本発明の特許範囲はこれに限定されない。
［実施例１］厚み２５０ミクロン以下の単面紙状面パール光沢合成紙
ポリプロピレン（ＭＦＩ：２．４）６７重量％、静電気防止剤３重量％を混合した後、ホッパーからサイドフィーダーを持つトゥイン・スクリュー主押出機に入れ、さらに炭酸カルシウム粉末２０重量％及び二酸化チタン１０重量％を計量後、それぞれフィーダーを持つトゥイン・スクリュー主押出機に入れる。また、ポリプロピレン（ＭＦＩ：５）６２重量％、ポリエチレン（ＭＦＩ：１）１２重量％、静電気防止剤２重量％、粘着防止剤３重量％、紫外線吸収剤１重量％をミキサーで混合した後、ホッパーからサイドフィーダーを持つトゥイン・スクリュー＃１副押出機に入れる。さらに炭酸カルシウム粉末１０重量％及び二酸化チタン１０重量％を計量後、それぞれ２つのフィーダーからトゥイン・スクリュー＃２副押出機に入れる。別に、ポリプロピレン（ＭＦＩ：２．４）９７重量％、粘着防止剤３重量％をミキサーで混合した後、ホッパーからサイドフィーダーを持つトゥイン・スクリュー＃２副押出機に入れる。押出機の温度を２００〜２８０℃に設定し、三層共押出方式によりＴダイヘッドから押出す。１５〜６０℃に設定された冷却ロールを経て、ポリプロピレンパール光沢合成紙板が冷却、成形される。成形された紙板は縦方向延伸装置に入れ、１２０〜１５０℃に加熱した後、縦方向に５倍延伸を行う。延伸後はアニーリングを行う。冷却後に再び横方向延伸装置に入れ、１５０〜１８５℃に加熱し、再び横方向に９倍延伸を行う。延伸後はアニーリングを行い、合成紙の収縮率を制御する。横方向延伸装置を出た後、コロナ処理装置に入れ、合成紙の印刷性を向上し、最後に巻取装置で巻き取る。上記の方法で得られた厚み２５０ミクロン以下の単面紙状面パール光沢合成紙は、筆記、印刷、包装およびその他の用途に汎用することができる。本実施例で選られた厚み６０ミクロン、１００ミクロン、１２０ミクロンの単面紙状面パール光沢合成紙の物性を表２に示す。
［実施例２］厚み２５０ミクロン以下の両面紙状面パール光沢合成紙
ポリプロピレン（ＭＦＩ：２．４）６８重量％、静電気防止剤２重量％を混合した後、ホッパーからサイドフィーダーを持つトゥイン・スクリュー主押出機に入れ、さらに炭酸カルシウム粉末１５重量％及び二酸化チタン１５重量％を計量後、それぞれ２つのフィーダーからトゥイン・スクリュー主押出機に入れる。また、ポリプロピレン（ＭＦＩ：５）５８重量％、ポリエチレン（ＭＦＩ：１）１２重量％、静電気防止剤２重量％、粘着防止剤３重量％、紫外線吸収剤１重量％をミキサーで混合した後、ホッパーからそれぞれ＃１、＃２のサイドフィーダーを持つトゥイン・スクリュー副押出機２台に入れる。さらに炭酸カルシウム粉末１２重量％及び二酸化チタン１２重量％を計量後、それぞれ２つのサイドフィーダーから＃１、＃２トゥイン・スクリュー副押出機に入れる。押出機の温度を２００〜２８０℃に設定し、三層共押出方式によりＴダイヘッドから押出す。２５〜６０℃に設定された冷却ロールを経て、ポリプロピレンパール光沢合成紙板が冷却、成形される。成形された紙板は縦方向延伸装置に入れ、１２０〜１５０℃に加熱した後、縦方向に４．５倍延伸を行う。延伸後はアニーリングを行う。冷却後に再び横方向延伸装置に入れ、１５５〜１９０℃に加熱し、再び横方向に８．５倍延伸を行う。延伸後はアニーリングを行い、合成紙の収縮率を制御する。横方向延伸装置を出た後、コロナ処理装置に入れ、合成紙の印刷性を向上し、最後に巻取装置で巻き取る。上記の方法で得られた厚み２５０ミクロン以下の両面紙状面パール光沢合成紙は、筆記、印刷、包装およびその他の用途に汎用することができる。本実施例で選られた厚み６０ミクロン、１００ミクロン、１５０ミクロンの両面紙状面パール光沢合成紙の物性を表３に示す。
［実施例３］厚み２５０ミクロン以下の両面光沢面パール光沢合成紙
ポリプロピレン（ＭＦＩ：２．４）６２重量％、静電気防止剤３重量％を混合した後、ホッパーからサイドフィーダーを持つトゥイン・スクリュー主押出機に入れ、さらに炭酸カルシウム粉末２０重量％及び二酸化チタン１５重量％を計量後、それぞれ２つのフィーダーからトゥイン・スクリュー主押出機に入れる。また、ポリプロピレン（ＭＦＩ：３．０）９６重量％、静電気防止剤２重量％、粘着防止剤２重量％をミキサーで混合した後、それぞれ＃１、＃２のサイドフィーダーを持つトゥイン・スクリュー副押出機に入れる。押出機の温度を２００〜２８０℃に設定し、三層共押出方式によりＴダイヘッドから押出す。１５〜６０℃に設定された冷却ロールを経て、ポリプロピレンパール光沢合成紙板が冷却、成形される。成形された紙板は縦方向延伸装置に入れ、１２０〜１５０℃に加熱した後、縦方向に５倍延伸を行う。延伸後はアニーリングを行う。冷却後に再び横方向延伸装置に入れ、１５０〜１８５℃に加熱し、再び横方向に９倍延伸を行う。延伸後はアニーリングを行い、合成紙の収縮率を制御する。横方向延伸装置を出た後、コロナ処理装置に入れ、合成紙の印刷性を向上し、最後に巻取装置で巻き取る。上記の方法で得られた厚み２５０ミクロン以下の両面光沢面パール光沢合成紙は、筆記、印刷、包装およびその他の用途に汎用することができる。本実施例で選られた厚み７０ミクロン、１１０ミクロン、１４０ミクロンの両面光沢面パール光沢合成紙の物性を表４に示す。
【０００８】
【発明の効果】
本発明の製造方法で得られた合成紙は、紙状層を縦方向に延伸したが、横方向延伸していないフィルムを一軸延伸層とする従来の製品とは、製造工程、使用原料の配合に関して大きな差がある。これにより、天然紙に取って代わり用途を広げることができ、以下の長所を持つ。
紙状層の原料はポリプロピレン、ポリエチレン、二酸化チタン、無機粉末を主成分とし、マッドな光沢を持ち、白色度と遮蔽度は従来の紙を上回る。
二軸延伸の紙状層は優れた剛性を持ち、無機粉末の定着性も良好で、印刷過程において粉末が脱落することはない。
紙状層及び樹脂層と発泡中間層は同じ延伸率を持ち、紙の収縮が均一となるため、加熱された面がウェーブ状に変形しにくい。また同じ延伸率を持つ紙状層と発泡中間層は剥離しにくい。
紙状層及び樹脂層の厚みは１〜３０ミクロンの範囲で副押出機からの押出量により制御することができる（製品の厚みは需要と用途により変化させることができる）。
製造工程の生産速度が速く、最大３．５トン／時間に達する。最大幅は８メートルで、厚みも２５〜２５０ミクロンと選択範囲が広い。
紙状層、樹脂層及び発泡中間層は側面にフィーダーを持つトゥイン・スクリュー押出機から押出され、原料の混練が均一なため、製品の厚みを±２％以内に制御することができる。押出機は粉末状の無機粉末を側面のフィーダーに入れることができるため、無機粉末の複合粒（マスターバッチ）だけを使用する必要がなく、原料コストを大幅に削減できる。このほか、無機粉末の複合粒を単ねじ棒押出機で生産することもできる。ただし、押出機のねじ棒のＬ／Ｄ率（長さ／直径）を高めて、原料の混練を均一にする必要がある。
生産コストが低く、市場競争力を有する。
【図面の簡単な説明】
【図１】三層共押出方式で得られる厚み２５〜２５０ミクロン二軸延伸ポリプロピレンパール光沢合成紙の三層構造（紙状層／発泡中間層／紙状層）
【図２】三層共押出方式で得られる厚み２５〜２５０ミクロン二軸延伸ポリプロピレンパール光沢合成紙の三層構造（紙状層／発泡中間層／樹脂層）
【図３】三層共押出方式で得られる厚み２５〜２５０ミクロン二軸延伸ポリプロピレンパール光沢合成紙の三層構造（樹脂層／発泡中間層／樹脂層）
【図４】本発明の製造装置説明図
押出機装置
冷却成形ロール装置
縦方向延伸装置
横方向延伸装置
コロナ処理装置
巻取装置
【表１】

【表２】

【表３】

【表４】

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method for producing a biaxially stretched polypropylene pearl gloss synthetic paper having a thickness of 25 to 250 microns obtained by a three-layer coextrusion method, and in particular, a twin-screw main extruder 1 each having a feeder by a three-layer coextrusion method. Combined polypropylene resin and inorganic mixed extrudate extruded from two twin screw sub-extruders with a base and a feeder, and through one T-die head a paper layer or resin layer / foamed intermediate layer / paper layer or The resin layer is formed into a three-layer sheet, which is further subjected to steps such as cooling molding, biaxial stretching, corona treatment, and winding, and the three layers of paper layer / foaming intermediate layer / paper layer having a thickness of 25 to 250 microns are obtained. Extruded double-sided paper-like pearly luster synthetic paper, three layers co-extruded single-sided paper-like pearly glossy synthetic paper, resin layer / foamed intermediate layer / resin layer To produce a three-layer coextrusion sided glossy surface pearlescent synthetic paper, it refers to those which the coating synthetic paper coated paper.
[0002]
[Prior art]
Currently, polyolefin synthetic paper is replacing natural pulp paper. A synthetic paper was filed and put into practical use, in which a biaxially oriented polypropylene film was used as a base layer (intermediate layer), and a polypropylene uniaxially oriented film containing 8 to 65% by weight of inorganic fine powder on both sides was used as a paper layer. Yes. Oji Oil Chemical Co., Ltd. has filed patent applications such as Japanese Patent Publication Nos. 46-40794, 56-141339, 56-118437 and 3-87255.
[0004]
[Problems to be solved by the invention]
In these production methods, a base material layer is placed between a longitudinal stretching device and a transverse stretching device, and two extruders are used to make upper and lower films to complete a paper layer. The paper layer can be stretched only in the transverse direction, and the strength of the paper layer is low. Since the inorganic fine powder added to enhance the printability of the paper-like layer falls off in the printing process, it is necessary to clean the printing equipment. In addition, the paper layer obtained by uniaxial stretching and the base material layer obtained by biaxial stretching have different total stretch ratios. It transforms into a wave shape. In order to further improve the stability of the manufacturing process and product quality, the production speed is limited in the manufacturing process of the paper-like layer in which the upper and lower films are completed with two extruders, and the width of the finished product after stretching is only 6 meters at maximum. Absent. Since the thickness of a single paper layer is required to be at least 10 microns (usually 30 microns), the thickness of the product will always be 60 microns or more. Otherwise, the thickness of the product becomes non-uniform and the printing process is affected. Overall, the difficulty of the manufacturing process is high and the production cost is high, so that the products are difficult to spread and difficult to apply.
[0005]
[Means for Solving the Problems]
In order to solve the above problem, the applicant of the present invention submits a new method for producing a three-layer synthetic paper. The synthetic paper is composed of a paper-like layer or resin layer / foamed intermediate layer / paper-like layer or resin layer, and a polypropylene resin mixture of the foamed intermediate layer is fed from a twin screw main extruder having one feeder, Alternatively, the resin mixture of the resin layer is extruded from a twin screw sub-extruder having two feeders, and these extrudates are merged to form a three-layer sheet through one T-die head, and further, cooling molding, biaxial stretching, Through steps such as corona treatment and winding, a three-layer coextruded single / double-sided paper-like surface and a double-sided glossy pearly glossy synthetic paper having a thickness of 25 to 250 microns are obtained. The production method of the present invention employs a three-layer coextrusion method. Synthetic paper obtained by joining the extrudates of each layer and then co-extrusion and biaxial rolling is a synthetic paper obtained by pasting a uniaxially stretched paper-like surface to a biaxially stretched intermediate layer by a conventional method. It differs from paper in structure and manufacturing method. At the same time, by selecting the raw material to be extruded from the sub-extruder from the paper layer using inorganic filler and the resin layer not containing inorganic filler, the three layers of paper layer / foaming intermediate layer / paper layer are combined. Extruded double-sided paper-like pearly glossy synthetic paper, paper layer / foamed intermediate layer / resin layer three-layer coextruded single-sided paper-like pearly glossy synthetic paper, resin layer / foamed intermediate layer / resin layer three-layer coextruded double-sided Glossy surface pearl glossy synthetic paper can be manufactured and used as a coated paper for synthetic paper for application.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In order to clearly show the technical contents of the present invention, the polypropylene resin mixture and the production process (extrusion, three-layer coextrusion, cooling, biaxial stretching, corona treatment, winding) will be described below. The biaxially oriented polypropylene pearl gloss synthetic paper of the present invention has a three-layer structure. The foamed intermediate layer is extruded with a twin screw main extruder having one side feeder. Highly crystalline polypropylene having an isotactic degree of 97% or more and 39 to 95% by weight and 1 to 5% by weight of an antistatic agent are uniformly stirred with a hopper located in front of the main extruder and put into the main extruder. Further, after 0 to 40% by weight of calcium carbonate powder and 0 to 20% by weight of titanium dioxide powder are weighed, they are put into the main extruder by one or two side feeders. After uniformly kneading with the twin screw of the main extruder, the mixture of resin and inorganic powder is pushed into the runner of the T-die head. The paper layer is extruded with two twin screw sub-extruders with side feeders. 20 to 99.5% by weight of polypropylene, 0 to 12% by weight of polyethylene, 0 to 3% by weight of antistatic agent, 0.5 to 3% by weight of anti-blocking agent, and 0 to 2% by weight of UV absorber are placed in front of the sub-extruder. After stirring uniformly with a certain hopper, it is put into a sub-extruder. Further, after 0 to 40% by weight of calcium carbonate powder and 0 to 20% by weight of titanium dioxide powder are weighed, they are put into a sub-extruder with one or two side feeders. After uniformly kneading with the twin screw of the sub-extruder, the mixture of resin and inorganic powder is pushed into both sides of the T-die head. The extrudates from the above three extruders are joined and coextruded with a T-die head to form a resin layer or paper layer / foamed intermediate layer / resin layer or paper layer sheet. Through the steps of biaxial stretching, corona treatment, and winding, a pearly glossy synthetic paper having a thickness of 20 to 250 microns and having both sides / single-sided paper is produced. Synthetic paper produced by the production method of the present invention is suitable for culture paper, and uses highly crystalline polypropylene as a main raw material. The polypropylene resin used in the present invention has a melt index (MFI) of 0.5 to 8 (230 ° C./2.16 kg ASTM D1238), and is mostly an isotactic homogeneous polymer. In this type of polymer structure, the molecules are bonded in a correct arrangement. The mechanical strength and quality uniformity of the pearly luster synthetic paper can be controlled by the molecular weight of the raw material and its distribution. The pearly luster synthetic paper obtained by the production method of the present invention has a three-layer structure. As shown in FIG. 1, in order to enhance the paper imitation effect of the paper layer, polyethylene and inorganic powder can be blended, and the glossiness, writing property, and printability can be adjusted by the dosage. Polyethylene having an MFI of 0.1 to 7 is employed. The strength of the paper surface can be adjusted with MFI of polyethylene. The inorganic powder used in the present invention lowers the density of the foamed intermediate layer (utilizes the generation of micropores in the stretching process), and can provide excellent writing properties and printability different from plastic paper in the paper-like layer. . One or more inorganic powders are selected from the group of calcium carbonate, diatomaceous earth, clay, calcium oxide, barium sulfate, titanium dioxide and the like. Its particle size is 0.1 to 10 microns and the dose is determined by the demand for the product. The present invention is manufactured with a twin screw extruder that feeds the compounding material from the side. The inorganic powder is put into the extruder from the side feeder. It can be uniformly kneaded with an extruder using a twin screw. In addition, it is also possible to put the composite particles obtained by previously kneading the inorganic powder and the resin into the foremost hopper, mix them with various resins, and then put them into an extruder. In the present invention, titanium dioxide powder is used to adjust the opacity, whiteness and anti-ultraviolet property of the product. The antistatic agent of this invention can use all the antistatic agents currently used with normal biaxially-stretched polypropylene (BOPP). Tertiary amines are mainly used. Tertiary amine has charge transferability, and can eliminate static electricity generated by processing friction. In the present invention, it is necessary to add an anti-tacking agent in order to adhere to each other when the synthetic paper is taken up. One type can be selected from silica, clay, polymethylacrylic acid methyl ester (PMMA), glass beads and the like used in ordinary biaxially oriented polypropylene. The specific gravity of the polypropylene pearl gloss synthetic paper obtained in the present invention is 0.75 or less, and can be adjusted by the composition ratio of the mixture. This is lower than 0.79 of the synthetic paper disclosed in JP-A-3-87255, and can produce a synthetic paper having a larger area with the same weight. The biaxially stretched polypropylene pearl gloss synthetic paper obtained in the present invention has a three-layer structure of paper layer / foamed intermediate layer / paper layer or resin layer, and the physical properties and production capacity are blended with materials, equipment, and operations. There is a deep relationship. The normal biaxially stretched product of polypropylene film is a transparent product with almost no filler added. In the present invention, in order to imitate paper, it is necessary to add a large amount of an inorganic filler in the production process, and the problems regarding the productivity, production capacity, and quality stability of the biaxial stretching production process must be overcome. FIG. 4 shows the manufacturing process apparatus and steps used for the polypropylene pearl gloss synthetic paper (thickness 25 to 250 microns) of the present invention.
Extruder device ((1) in FIG. 4): Consists of one twin-screw main extruder with side feeders and two twin-screw sub-extruders with side feeders. The temperature setting condition varies depending on the composition of the resin mixture, MFI, crystallinity, viscosity, production line speed, and product thickness, but is usually 180 to 280 ° C. Below 180 ° C., the plasticization of the resin does not proceed and it cannot be extruded with a T-die head. If it is 280 ° C. or higher, the resin is excessively plasticized and cracks. In the present invention, three-layer synthetic paper (paper-like layer or resin layer / foamed intermediate layer / paper-like layer or resin layer) is produced by a three-layer coextrusion method. Three layers of extrudates are merged by the flow path design of the T die head, and the three layers are coextruded with the T die head.
Cooling roll device ((2) in FIG. 4): A water-cooled or gas-cooled cooling device. The melt coextrudate that has been three-layer coextruded at 180 to 280 ° C. is cooled and molded. Control of the cooling temperature has a great influence on whether or not the subsequent steps go smoothly. The cooling temperature is usually set to 15 to 60 ° C. and can be adjusted within this range depending on the thickness of the synthetic paper board and the speed of the production line.
Longitudinal stretching apparatus ((3) in FIG. 4): The paper board that has undergone cooling molding is placed in the longitudinal stretching apparatus. First, it is heated to 115 to 150 ° C. (selected by the thickness of the paper board and the speed of the production line) to soften the paper board, and further stretched in two stages, low speed and high speed, to give longitudinal strength to the synthetic paper. Moreover, it shape | molds by annealing. The stretching ratio in the longitudinal direction is usually set to 3 to 6 times.
Transverse stretching device ((4) in FIG. 4): The paper board thinned by the longitudinal stretching process is heated to 140 to 195 ° C. (selected according to the thickness of the paper board and the production line speed) and softened in the lateral direction. Stretched and then molded by annealing, and the size stability is enhanced by partial shrinkage of pearl synthetic paper. Usually, a transverse direction draw ratio is set to 5 to 12 times. You can choose according to the characteristics of the product.
Corona treatment device ((5) in FIG. 4): Corona treatment is performed to improve the physical properties of polypropylene pearl gloss synthetic paper and facilitates processing such as printing, coating, and coating. Corona treatment is performed with a high-frequency discharge device (adjusted according to the speed of the production line) with a treatment efficiency of 20 to 120 KW. This reaches a surface wet tension of 36-48 dynes / cm.
Winding device ((6) in FIG. 4): Using a steel pipe, the finished pearl gloss synthetic paper is wound to make a finished product having a width of 8 meters. If necessary, cut vertically or horizontally and wrap the resulting product into a roll or sheet product having a thickness of 25 to 250 microns. Table 1 shows the thickness of three layers in the biaxially stretched polypropylene pearl gloss synthetic paper having a thickness of 25 to 250 microns obtained by the production method of the present invention. The thickness of the paper layer and the resin layer can be adjusted in the range of 1 to 30 microns.
[0007]
In order to clearly explain the technical contents of the present invention, examples of the present invention in which synthetic paper for writing, printing, packaging and various uses are produced are shown below. However, the patent scope of the present invention is not limited to this.
[Example 1] Single-sided paper-like surface pearly luster synthetic paper polypropylene (MFI: 2.4) 67% by weight with a thickness of 250 microns or less and 3% by weight of an antistatic agent were mixed, and then a twine having a side feeder from a hopper It puts into a screw main extruder, and after weighing 20% by weight of calcium carbonate powder and 10% by weight of titanium dioxide, it is put into a twin screw main extruder having a feeder. In addition, 62% by weight of polypropylene (MFI: 5), 12% by weight of polyethylene (MFI: 1), 2% by weight of antistatic agent, 3% by weight of anti-blocking agent, and 1% by weight of UV absorber were mixed with a mixer, and then a hopper Into a twin screw # 1 sub-extruder with a side feeder. Further, 10% by weight of calcium carbonate powder and 10% by weight of titanium dioxide are weighed and then fed into the twin screw # 2 sub-extruder from two feeders. Separately, 97% by weight of polypropylene (MFI: 2.4) and 3% by weight of an anti-blocking agent are mixed by a mixer, and then, the hopper is put into a twin screw # 2 sub-extruder having a side feeder. The temperature of the extruder is set to 200 to 280 ° C., and extrusion is performed from the T die head by a three-layer coextrusion method. The polypropylene pearl gloss synthetic paper board is cooled and molded through a cooling roll set at 15 to 60 ° C. The formed paper board is put in a longitudinal stretching apparatus, heated to 120 to 150 ° C., and then stretched 5 times in the longitudinal direction. After stretching, annealing is performed. After cooling, it is again put in a transverse stretching apparatus, heated to 150 to 185 ° C., and again stretched 9 times in the transverse direction. After stretching, annealing is performed to control the shrinkage rate of the synthetic paper. After leaving the transverse stretching device, it is placed in a corona treatment device to improve the printability of the synthetic paper, and is finally wound by a winding device. The single-sided paper-like surface pearly luster synthetic paper having a thickness of 250 microns or less obtained by the above method can be widely used for writing, printing, packaging and other uses. Table 2 shows the physical properties of the single-sided paper-like pearly luster synthetic paper having thicknesses of 60 microns, 100 microns, and 120 microns selected in this example.
[Example 2] A twin screw having a side feeder from a hopper after mixing 68% by weight of double-sided paper-like pearly luster synthetic paper polypropylene (MFI: 2.4) with a thickness of 250 microns or less and 2% by weight of an antistatic agent. Into the main extruder, 15% by weight of calcium carbonate powder and 15% by weight of titanium dioxide are weighed and then fed into the twin screw main extruder from two feeders. In addition, 58% by weight of polypropylene (MFI: 5), 12% by weight of polyethylene (MFI: 1), 2% by weight of antistatic agent, 3% by weight of anti-blocking agent, and 1% by weight of UV absorber were mixed with a mixer, and then a hopper Into two twin screw sub-extruders with # 1 and # 2 side feeders, respectively. Further, 12% by weight of calcium carbonate powder and 12% by weight of titanium dioxide are weighed and then put into # 1 and # 2 twin screw sub-extruders from two side feeders, respectively. The temperature of the extruder is set to 200 to 280 ° C., and extrusion is performed from a T-die head by a three-layer coextrusion method. The polypropylene pearl gloss synthetic paper board is cooled and molded through a cooling roll set at 25 to 60 ° C. The formed paper board is put into a longitudinal stretching device, heated to 120 to 150 ° C., and then stretched 4.5 times in the longitudinal direction. After stretching, annealing is performed. After cooling, it is again put in a transverse stretching apparatus, heated to 155 to 190 ° C., and stretched 8.5 times in the transverse direction again. After stretching, annealing is performed to control the shrinkage rate of the synthetic paper. After leaving the transverse stretching device, it is placed in a corona treatment device to improve the printability of the synthetic paper, and is finally wound by a winding device. The double-sided paper-like pearly luster synthetic paper having a thickness of 250 microns or less obtained by the above method can be widely used for writing, printing, packaging and other uses. Table 3 shows the physical properties of the double-sided paper-like pearly luster synthetic paper of thickness 60 microns, 100 microns, and 150 microns selected in this example.
[Embodiment 3] Twin screw main having a side feeder from a hopper after mixing 62 wt% of pearl gloss synthetic paper polypropylene (MFI: 2.4) with a thickness of 250 microns or less and 3 wt% of an antistatic agent It puts into an extruder and weighs 20% by weight of calcium carbonate powder and 15% by weight of titanium dioxide, and then puts them into a twin screw main extruder from two feeders. In addition, 96 wt% of polypropylene (MFI: 3.0), 2 wt% of antistatic agent, and 2 wt% of antistatic agent were mixed in a mixer, and then twin screw sub-extrusion with side feeders # 1 and # 2 respectively. Put in the machine. The temperature of the extruder is set to 200 to 280 ° C., and extrusion is performed from the T die head by a three-layer coextrusion method. The polypropylene pearl gloss synthetic paper board is cooled and molded through a cooling roll set at 15 to 60 ° C. The formed paper board is put in a longitudinal stretching apparatus, heated to 120 to 150 ° C., and then stretched 5 times in the longitudinal direction. After stretching, annealing is performed. After cooling, it is again placed in a transverse stretching apparatus, heated to 150 to 185 ° C., and again stretched 9 times in the transverse direction. After stretching, annealing is performed to control the shrinkage rate of the synthetic paper. After leaving the transverse stretching device, it is placed in a corona treatment device to improve the printability of the synthetic paper, and is finally wound by a winding device. The double-sided glossy pearly luster synthetic paper having a thickness of 250 microns or less obtained by the above method can be used for writing, printing, packaging and other applications. Table 4 shows the physical properties of the double-sided glossy pearly glossy synthetic paper of thicknesses 70 microns, 110 microns, and 140 microns selected in this example.
[0008]
【The invention's effect】
Synthetic paper obtained by the production method of the present invention is a conventional product in which a paper-like layer is stretched in the longitudinal direction but a film that is not stretched in the transverse direction is a uniaxially stretched layer. There is a big difference regarding. As a result, it can be used in place of natural paper and expanded, and has the following advantages.
The raw material of the paper layer is composed mainly of polypropylene, polyethylene, titanium dioxide, and inorganic powder, has a mad luster, and has a whiteness and shielding degree higher than those of conventional paper.
The biaxially stretched paper-like layer has excellent rigidity and good fixability of the inorganic powder, and the powder does not fall off during the printing process.
Since the paper layer, the resin layer, and the foamed intermediate layer have the same stretch ratio and the shrinkage of the paper is uniform, the heated surface is not easily deformed into a wave shape. Moreover, the paper-like layer and the foamed intermediate layer having the same stretch ratio are difficult to peel off.
The thickness of the paper-like layer and the resin layer can be controlled by the extrusion amount from the sub-extruder in the range of 1 to 30 microns (the product thickness can be changed according to demand and application).
The production speed of the manufacturing process is fast, reaching a maximum of 3.5 tons / hour. The maximum width is 8 meters and the thickness is 25-250 microns, so the selection range is wide.
The paper layer, the resin layer, and the foamed intermediate layer are extruded from a twin screw extruder having a feeder on the side surface, and since the raw materials are uniformly kneaded, the thickness of the product can be controlled within ± 2%. Since the extruder can put powdered inorganic powder into the feeder on the side surface, it is not necessary to use only composite particles (master batch) of inorganic powder, and the raw material cost can be greatly reduced. In addition, composite particles of inorganic powder can be produced with a single screw rod extruder. However, it is necessary to increase the L / D ratio (length / diameter) of the screw rod of the extruder so that the raw materials are uniformly kneaded.
Low production cost and competitiveness in the market.
[Brief description of the drawings]
1 is a three-layer structure (paper-like layer / foaming intermediate layer / paper-like layer) of a biaxially oriented polypropylene pearl gloss synthetic paper having a thickness of 25 to 250 microns obtained by a three-layer coextrusion method.
Fig. 2 Three-layer structure of biaxially oriented polypropylene pearl gloss synthetic paper with a thickness of 25 to 250 microns obtained by a three-layer coextrusion method (paper-like layer / foamed intermediate layer / resin layer)
FIG. 3 shows a three-layer structure (resin layer / foamed intermediate layer / resin layer) of a biaxially stretched polypropylene pearl gloss synthetic paper having a thickness of 25 to 250 microns obtained by a three-layer coextrusion method.
FIG. 4 is an explanatory diagram of a production apparatus of the present invention, an extruder apparatus, a cooling forming roll apparatus, a longitudinal stretching apparatus, a transverse stretching apparatus, a corona treatment apparatus, a winding apparatus.

[Table 2]

[Table 3]

[Table 4]

Claims

In a method for producing a 25-250 micron biaxially oriented polypropylene (BOPP) pearl gloss synthetic paper obtained by a three-layer coextrusion method, a highly crystalline polypropylene having an isotactic degree of 97% or more (MFI: 0.5-8) Polypropylene resin mixture comprising 39 to 95% by weight and calcium carbonate powder 0 to 40% by weight, titanium dioxide 0 to 20% by weight, antistatic agent 1 to 5% by weight, polypropylene 22 to 99.5% by weight, polyethylene resin 0 -12 wt%, titanium dioxide powder 0-20 wt%, calcium carbonate powder 0-40 wt%, antistatic agent 0-3 wt%, anti-blocking agent 0.5-3 wt%, UV absorber 0- 2 wt% resin mixture, one twin-screw main extruder each with side feeder and tween with side feeder・ Put each of the screw sub-extruders from two hoppers and feeders, set the extruder temperature to 180-280 ° C, and after extrusion, extrude from the T-die head to make a pearl gloss synthetic paper sheet with a cooling roll of 15-60 ° C After cooling, forming, and then biaxially stretching the paper sheet , heating to 115-150 ° C , stretching, annealing, stretching in the machine direction 3-6 times, and further heating to 140-195 ° C, stretching, The film is annealed and stretched 5 to 12 times in the transverse direction, then subjected to a high-frequency corona treatment with an efficiency of 20 to 120 KW, wound by a winder, and a paper layer / foamed intermediate layer / thickness layer of 25 to 250 microns paper-like layer, the paper-like layer / foamed intermediate layer / resin layer, characterized in that the three three-layer co-extruded polypropylene pearlescent synthetic paper of the resin layer / foamed intermediate layer / the resin layer, Method for producing 25-250 Milon biaxially oriented polypropylene pearlescent synthetic paper thickness obtained with a layer coextrusion method.